Previously, hydraulic brake systems with slip control have exclusively been conceived as multi-circuit, preferably dual-circuit, brake systems. A satisfactory deceleration of the vehicle, which is in conformity with legal regulations for brake systems, is achieved due to the given redundance of brake circuits in the event of brake circuit leakage. In this respect, reference is made to the source of literature "BOSCH Technische Unterrichtung" (technical instructions), automotive vehicle brake systems, Robert Bosch GmbH, first edition of September 1989.
Although legal regulations for passenger vehicles in Europe and the U.S. so far do not mandate the provision of multiple circuits in brake systems, multiple circuit systems are the norm. A multiple-circuit brake system is relatively complicated and expensive, especially with respect to an application for anti-lock and/or traction slip control. Further, the complexity of such hydraulic brake systems with slip control involves a great number of possible malfunctions, which should not be underestimated. Such malfunctions are mainly due to leakages of the pump, the braking pressure generator and the pressure modulation valves.